The Barrington Tops Batholith (BTB) is an Early Permian, granodioritic suite intruding the Tamworth Belt in the Southern New England Fold Belt (SNEFB), as shown in Fig. 1. It is composed of three plutons of two comagmatic compositions: the two larger plutons, Omadale Brook and Barrington River, are augitehypersthene granodiorite, while the Gummi Plain pluton, to the north-east is a hornblende-biotite granodiorite (Mason and Kaverlieris 1984; Eggins and Hensen 1987). In addition to the granodiorites, Eggins (1984) notes the presence of several phases of dyke and stock intrusion. Two phases of mafic dykes are associated with the plutons, one intruding before the plutons, and one after. In addition, aplitic and microgranodioritic dykes of similar mineralogy to the main suite are known. These felsic intrusives are noted on the margins of the intrusions and are seen in both the granodiorites and their surrounding aureole. Finally, Eggins (1984) notes the presence of quartz diorite intrusives in several locations around the BTB. However, poor outcrop means that the relationship between these and the other intrusives has not been discerned.